[176] | 1 | // -*- C++ -*- |
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| 2 | |
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| 3 | #ifndef _EMPTYCLASS_H_ |
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| 4 | #define _EMPTYCLASS_H_ |
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| 5 | |
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| 6 | #include <stdio.h> // for stderr |
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| 7 | #include "check.h" |
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| 8 | #include "array.h" |
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| 9 | #include "hldefines.h" |
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| 10 | |
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| 11 | /** |
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| 12 | * @class EmptyClass |
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| 13 | * @brief Maintains superblocks organized by emptiness. |
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| 14 | */ |
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| 15 | |
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| 16 | namespace Hoard { |
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| 17 | |
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| 18 | template <class SuperblockType_, |
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| 19 | int EmptinessClasses> |
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| 20 | class EmptyClass { |
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| 21 | |
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| 22 | enum { SuperblockSize = sizeof(SuperblockType_) }; |
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| 23 | |
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| 24 | public: |
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| 25 | |
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| 26 | typedef SuperblockType_ SuperblockType; |
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| 27 | |
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| 28 | EmptyClass (void) |
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| 29 | { |
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| 30 | for (int i = 0; i <= EmptinessClasses + 1; i++) { |
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| 31 | _available(i) = 0; |
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| 32 | } |
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| 33 | } |
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| 34 | |
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| 35 | void dumpStats (void) { |
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| 36 | for (int i = 0; i <= EmptinessClasses + 1; i++) { |
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| 37 | SuperblockType * s = _available(i); |
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| 38 | if (s) { |
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| 39 | fprintf (stderr, "EmptyClass: emptiness class = %d\n", i); |
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| 40 | while (s) { |
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| 41 | s->dumpStats(); |
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| 42 | s = s->getNext(); |
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| 43 | } |
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| 44 | } |
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| 45 | } |
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| 46 | } |
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| 47 | |
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| 48 | |
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| 49 | SuperblockType * getEmpty (void) { |
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| 50 | Check<EmptyClass, MyChecker> check (this); |
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| 51 | SuperblockType * s = _available(0); |
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| 52 | if (s && |
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| 53 | (s->getObjectsFree() == s->getTotalObjects())) { |
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| 54 | // Got an empty one. Remove it. |
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| 55 | _available(0) = s->getNext(); |
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| 56 | if (_available(0)) { |
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| 57 | _available(0)->setPrev (0); |
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| 58 | } |
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| 59 | s->setPrev (0); |
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| 60 | s->setNext (0); |
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| 61 | return s; |
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| 62 | } |
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| 63 | return 0; |
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| 64 | } |
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| 65 | |
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| 66 | SuperblockType * get (void) { |
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| 67 | Check<EmptyClass, MyChecker> check (this); |
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| 68 | // Return as empty a superblock as possible |
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| 69 | // by iterating from the emptiest to the fullest available class. |
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| 70 | for (int n = 0; n < EmptinessClasses + 1; n++) { |
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| 71 | SuperblockType * s = _available(n); |
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| 72 | while (s) { |
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| 73 | assert (s->isValidSuperblock()); |
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| 74 | // Got one. Remove it. |
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| 75 | _available(n) = s->getNext(); |
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| 76 | if (_available(n)) { |
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| 77 | _available(n)->setPrev (0); |
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| 78 | } |
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| 79 | s->setPrev (0); |
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| 80 | s->setNext (0); |
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| 81 | |
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| 82 | #ifndef NDEBUG |
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| 83 | // Verify that this superblock is *gone* from the lists. |
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| 84 | for (int z = 0; z < EmptinessClasses + 1; z++) { |
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| 85 | SuperblockType * p = _available(z); |
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| 86 | while (p) { |
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| 87 | assert (p != s); |
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| 88 | p = p->getNext(); |
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| 89 | } |
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| 90 | } |
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| 91 | #endif |
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| 92 | |
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| 93 | // Ensure that we return a superblock that is as free as |
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| 94 | // possible. |
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| 95 | int cl = getFullness (s); |
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| 96 | if (cl > n) { |
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| 97 | put (s); |
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| 98 | SuperblockType * sNew = _available(n); |
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| 99 | assert (s != sNew); |
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| 100 | s = sNew; |
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| 101 | } else { |
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| 102 | return s; |
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| 103 | } |
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| 104 | } |
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| 105 | } |
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| 106 | return 0; |
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| 107 | } |
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| 108 | |
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| 109 | void put (SuperblockType * s) { |
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| 110 | Check<EmptyClass, MyChecker> check (this); |
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| 111 | |
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| 112 | #ifndef NDEBUG |
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| 113 | // Check to verify that this superblock is not already on one of the lists. |
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| 114 | for (int n = 0; n <= EmptinessClasses + 1; n++) { |
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| 115 | SuperblockType * p = _available(n); |
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| 116 | while (p) { |
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| 117 | assert (p != s); |
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| 118 | p = p->getNext(); |
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| 119 | } |
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| 120 | } |
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| 121 | #endif |
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| 122 | |
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| 123 | // Put on the appropriate available list. |
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| 124 | int cl = getFullness (s); |
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| 125 | |
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| 126 | // printf ("put %x, cl = %d\n", s, cl); |
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| 127 | s->setPrev (0); |
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| 128 | s->setNext (_available(cl)); |
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| 129 | if (_available(cl)) { |
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| 130 | _available(cl)->setPrev (s); |
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| 131 | } |
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| 132 | _available(cl) = s; |
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| 133 | } |
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| 134 | |
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| 135 | INLINE MALLOC_FUNCTION void * malloc (size_t sz) { |
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| 136 | // Malloc from the fullest superblock first. |
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| 137 | for (int i = EmptinessClasses; i >= 0; i--) { |
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| 138 | SuperblockType * s = _available(i); |
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| 139 | // printf ("i\n"); |
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| 140 | if (s) { |
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| 141 | int oldCl = getFullness (s); |
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| 142 | void * ptr = s->malloc (sz); |
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| 143 | int newCl = getFullness (s); |
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| 144 | if (ptr) { |
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| 145 | if (oldCl != newCl) { |
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| 146 | transfer (s, oldCl, newCl); |
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| 147 | } |
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| 148 | return ptr; |
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| 149 | } |
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| 150 | } |
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| 151 | } |
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| 152 | return NULL; |
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| 153 | } |
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| 154 | |
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| 155 | INLINE void free (void * ptr) { |
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| 156 | Check<EmptyClass, MyChecker> check (this); |
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| 157 | SuperblockType * s = getSuperblock (ptr); |
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| 158 | int oldCl = getFullness (s); |
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| 159 | s->free (ptr); |
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| 160 | int newCl = getFullness (s); |
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| 161 | |
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| 162 | if (oldCl != newCl) { |
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| 163 | // Transfer. |
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| 164 | transfer (s, oldCl, newCl); |
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| 165 | } |
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| 166 | } |
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| 167 | |
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| 168 | /// Find the superblock (by bit-masking) that holds a given pointer. |
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| 169 | static INLINE SuperblockType * getSuperblock (void * ptr) { |
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| 170 | return SuperblockType::getSuperblock (ptr); |
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| 171 | } |
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| 172 | |
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| 173 | private: |
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| 174 | |
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| 175 | void transfer (SuperblockType * s, int oldCl, int newCl) |
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| 176 | { |
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| 177 | SuperblockType * prev = s->getPrev(); |
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| 178 | SuperblockType * next = s->getNext(); |
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| 179 | if (prev) { prev->setNext (next); } |
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| 180 | if (next) { next->setPrev (prev); } |
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| 181 | if (s == _available(oldCl)) { |
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| 182 | assert (prev == 0); |
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| 183 | _available(oldCl) = next; |
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| 184 | } |
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| 185 | s->setNext (_available(newCl)); |
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| 186 | s->setPrev (0); |
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| 187 | if (_available(newCl)) { _available(newCl)->setPrev (s); } |
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| 188 | _available(newCl) = s; |
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| 189 | } |
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| 190 | |
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| 191 | static INLINE int getFullness (SuperblockType * s) { |
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| 192 | // Completely full = EmptinessClasses + 1 |
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| 193 | // Completely empty (all available) = 0 |
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| 194 | int total = s->getTotalObjects(); |
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| 195 | int free = s->getObjectsFree(); |
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| 196 | if (total == free) { |
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| 197 | return 0; |
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| 198 | } else { |
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| 199 | return 1 + (EmptinessClasses * (total - free)) / total; |
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| 200 | } |
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| 201 | } |
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| 202 | |
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| 203 | /// Forward declarations for the sanity checker. |
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| 204 | /// @sa Check |
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| 205 | class MyChecker; |
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| 206 | friend class MyChecker; |
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| 207 | |
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| 208 | /// Precondition and postcondition checking. |
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| 209 | class MyChecker { |
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| 210 | public: |
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| 211 | #ifndef NDEBUG |
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| 212 | static void precondition (EmptyClass * e) { |
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| 213 | e->sanityCheckPre(); |
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| 214 | } |
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| 215 | static void postcondition (EmptyClass * e) { |
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| 216 | e->sanityCheck(); |
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| 217 | } |
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| 218 | #else |
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| 219 | static void precondition (EmptyClass *) {} |
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| 220 | static void postcondition (EmptyClass *) {} |
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| 221 | #endif |
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| 222 | }; |
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| 223 | |
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| 224 | void sanityCheckPre (void) { sanityCheck(); } |
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| 225 | |
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| 226 | void sanityCheck (void) { |
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| 227 | for (int i = 0; i <= EmptinessClasses + 1; i++) { |
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| 228 | SuperblockType * s = _available(i); |
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| 229 | while (s) { |
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| 230 | assert (getFullness(s) == i); |
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| 231 | s = s->getNext(); |
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| 232 | } |
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| 233 | } |
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| 234 | } |
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| 235 | |
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| 236 | /// The bins of superblocks, by emptiness class. |
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| 237 | /// @note index 0 = completely empty, EmptinessClasses + 1 = full |
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| 238 | Array<EmptinessClasses + 2, SuperblockType *> _available; |
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| 239 | |
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| 240 | }; |
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| 241 | |
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| 242 | } |
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| 243 | |
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| 244 | |
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| 245 | #endif |
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